Annular bearings are commonplace in a wide variety of industries. A representative annular bearing comprises an outer ring and an inner ring concentrically disposed within the outer ring. The inner and outer rings cooperate to form an annular raceway in which a plurality of rolling elements resides. The rolling elements may be, for example, ball bearings or roller bearings of various types (e.g., cylindrical roller bearings, tapered roller bearings, spherical roller bearings, etc). The rolling elements may be arranged into one or more rows. In a single row ball bearing, the raceway is substantially defined by a first annular groove provided in the inner surface of the outer ring (i.e., the outer race) and a second annular groove provided in the outer surface of the inner ring (i.e., the inner race). As the inner and outer rings rotate relative to one another, the ball bearings roll along the inner and outer races. Certain ball bearings, commonly referred to as Conrad bearings, further comprise an annular retainer or cage that resides between the inner ring and the outer ring to help guide and separate the rolling elements. The cage may comprise, for example, a unitary ring having a plurality of tubular pockets therein that each receives a different rolling element. Alternatively, the cage may comprise two undulating rings each having a plurality of hemispherical pockets therein. When the two rings are joined together via fasteners (e.g., rivets), the hemispherical pockets cooperate to form a series of spherical cavities, each of which holds a different one of the ball bearings.
In valve assemblies, annular bearings are often utilized to mount a rotatable shaft in the valve's flowbody housing. For example, a butterfly valve assembly may comprise a valve housing having a flow passage or conduit therethrough, a rotatable shaft mounted in the housing, and a valve element (e.g., a valve plate) coupled to the rotatable shaft and disposed within the conduit. One or more annular bearing are threaded over the shaft and positioned adjacent the housing (e.g., within cylindrical recesses provided within the housing). The inner ring of each annular bearing is then coupled to the shaft, and the outer ring of each annular bearing is coupled to the housing. As a result of this configuration, the inner bearing rotates along with the shaft, and the outer ring remains stationary. In this manner, the annular bearings may secure the shaft within the valve's housing, while simultaneously permitting the shaft to freely rotate.
In many applications, the fluid flowing through the flow passage or conduit will be contaminated with debris. For example, if the valve assembly is disposed on an aircraft, the conduit may conduct hot air (e.g., upwards of 1000 to 1200 degrees Fahrenheit) that carries dirt, sand, and/or other granulated debris. During valve operation, debris gradually accumulates in the bearing's raceway and impedes the movement of the rolling elements. This typically occurs when a seal disposed proximate the bearing fails and new flow passages are created through the bearing and raceway, although bearing contamination may also occur during other routine stages of valve operation (e.g., during start-up). As a consequence of bearing contamination, the degree of torque required to rotate the inner ring relative to the outer ring, and therefore to rotate the shaft relative to the housing, gradually increases. Ultimately, this may result in difficultly rotating the valve plate between its open and closed positions and a substantial decrease in valve reliability. Though seals and axial shields have been employed to physically block debris from entering the raceway, the utilization of seals and axial shields do not adequately deter the accumulation of debris and may, in fact, promote the accumulation of debris by preventing collected debris from readily escaping the raceway.
Considering the above, it should be appreciated that it would be desirable to provide a bearing having at least one flow bypass channel therethrough that substantially decrease the accumulation of debris within the bearing's raceway. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.